The applicability of microbially induced calcite precipitation (MICP) for internal erosion control in gravel-sand mixtures

Seepage-induced internal erosion in earth-filled embankment dams has been attracting the attention of civil engineering researchers and practitioners for decades. Microbially induced carbonate precipitation (MICP), owing to its proved performance in soil enhancement and permeability control, can potentially be used for internal erosion control. This paper examines the applicability of MICP for internal erosion control in gravel-sand mixtures using a large one-dimensional column test apparatus which incorporates the implementation of MICP. Visual observations, erosion characteristics and hydro-mechanical behaviours of non-MICP and MICP treated gravel-sand mixtures were investigated through a series of constant-pressure erosion tests. Test results confirm that MICP treatment can reduce the cumulative erosion weight, erosion rate and axial strain relative to non-MICP soil. The magnitudes of hydraulic conductivity for all tested samples before the erosion process fall into a range from 5.5 x 10(-5) to 8.0 x 10(-3) m/s. After the erosion process, non-MICP soils and MICP treated soils with low cementation concentrations experience a significant increase in hydraulic conductivity. Furthermore, a hydro-mechanical coupling analysis was conducted and different erosion modes were identified for low and high concentrations of cementation solution. Fundamentally, the efficiency of internal erosion reduction is controlled by the calcium carbonate precipitation content within the tested soils. Higher precipitation content can facilitate the formation of larger clusters of cemented sand particles, thus reducing the likelihood of erosion.